Expandable fusion device and method of installation thereof

ABSTRACT

The present invention provides an expandable fusion device capable of being installed inside an intervertebral disc space to maintain normal disc spacing and restore spinal stability, thereby facilitating an intervertebral fusion. In one embodiment, the fusion device includes a central ramp, a first endplate, and a second endplate, the central ramp capable of being moved in a first direction to move the first and second endplates outwardly and into an expanded configuration. The fusion device is capable of being deployed down an endoscopic tube.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention is a continuation application of U.S. patentapplication Ser. No. 12/875,706 filed on Sep. 3, 2010, which isincorporated in its entirety herein.

FIELD OF THE INVENTION

The present invention relates to the apparatus and method for promotingan intervertebral fusion, and more particularly relates to an expandablefusion device capable of being inserted between adjacent vertebrae tofacilitate the fusion process.

BACKGROUND OF THE INVENTION

A common procedure for handling pain associated with intervertebraldiscs that have become degenerated due to various factors such as traumaor aging is the use of intervertebral fusion devices for fusing one ormore adjacent vertebral bodies. Generally, to fuse the adjacentvertebral bodies, the intervertebral disc is first partially or fullyremoved. An intervertebral fusion device is then typically insertedbetween neighboring vertebrae to maintain normal disc spacing andrestore spinal stability, thereby facilitating an intervertebral fusion.

There are a number of known conventional fusion devices andmethodologies in the art for accomplishing the intervertebral fusion.These include screw and rod arrangements, solid bone implants, andfusion devices which include a cage or other implant mechanism which,typically, is packed with bone and/or bone growth inducing substances.These devices are implanted between adjacent vertebral bodies in orderto fuse the vertebral bodies together, alleviating the associated pain.

However, there are drawbacks associated with the known conventionalfusion devices and methodologies. For example, present methods forinstalling a conventional fusion device often require that the adjacentvertebral bodies be distracted to restore a diseased disc space to itsnormal or healthy height prior to implantation of the fusion device. Inorder to maintain this height once the fusion device is inserted, thefusion device is usually dimensioned larger in height than the initialdistraction height. This difference in height can make it difficult fora surgeon to install the fusion device in the distracted intervertebralspace.

As such, there exists a need for a fusion device capable of beinginstalled inside an intervertebral disc space at a minimum to nodistraction height and for a fusion device that can maintain a normaldistance between adjacent vertebral bodies when implanted.

SUMMARY OF THE INVENTION

In an exemplary embodiment, the present invention provides an expandablefusion device capable of being installed inside an intervertebral discspace to maintain normal disc spacing and restore spinal stability,thereby facilitating an intervertebral fusion. In one embodiment, thefusion device includes a central ramp, a first endplate, and a secondendplate. The central ramp may be capable of moving in a first directionto push the first and second endplates outwardly and into an unexpandedconfiguration. The expandable fusion device may be capable of beingplaced into the disc space down an endoscopic tube and then expandedinto an expanded configuration.

Further areas of applicability of the present invention will becomeapparent from the detailed description provided hereinafter. It shouldbe understood that the detailed description and specific examples, whileindicating the preferred or exemplary embodiments of the invention, areintended for purposes of illustration only and are not intended to limitthe scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 is a side view of an embodiment of an expandable fusion deviceshown between adjacent vertebrae according to the present invention;

FIG. 2 is a front perspective view of the expandable fusion device ofFIG. 1 shown in an unexpanded position in accordance with one embodimentof the present invention;

FIG. 3 is a front perspective view of the expandable fusion device ofFIG. 1 shown in an expanded position in accordance with one embodimentof the present invention;

FIG. 4 is a rear perspective view of the expandable fusion device ofFIG. 1 shown in an unexpanded position in accordance with one embodimentof the present invention;

FIG. 5 is a rear perspective view of the expandable fusion device ofFIG. 1 shown in an expanded position in accordance with one embodimentof the present invention;

FIG. 6 is a side view of the expandable fusion device of FIG. 1 shown inan unexpanded position in accordance with one embodiment of the presentinvention;

FIG. 7 is a side view of the expandable fusion device of FIG. 1 shown inan expanded position in accordance with one embodiment of the presentinvention;

FIG. 8 is a perspective view of the central ramp of the expandablefusion device of FIG. 1 in accordance with one embodiment of the presentinvention;

FIG. 9 is a perspective view of the driving ramp of the expandablefusion device of FIG. 1 in accordance with one embodiment of the presentinvention;

FIG. 10 is a perspective of an endplate of the expandable fusion deviceof FIG. 1 in accordance with one embodiment of the present invention;

FIG. 11 a perspective view showing placement of the first endplate of anembodiment of an expandable fusion device down an endoscopic tube andinto the disc space in accordance with one embodiment of the presentinvention;

FIG. 12 is a perspective view showing placement of the second endplateof the expandable fusion device down an endoscopic tube and into thedisc space in accordance with one embodiment of the present invention;

FIG. 13 is a perspective view showing placement of the central ramp ofthe expandable fusion device down an endoscopic tube and into the discspace in accordance with one embodiment of the present invention;

FIG. 14 is a perspective view showing expansion of the expandable fusiondevice in accordance with one embodiment of the present invention;

FIG. 15 is a side schematic view of the expandable fusion device of FIG.1 having different endplates;

FIG. 16 is a partial side schematic view of the expandable fusion deviceof FIG. 1 showing different modes of endplate expansion;

FIG. 17 is a side schematic view of the expandable fusion device of FIG.1 with artificial endplates shown between adjacent vertebrae;

FIG. 18 is a front perspective view of an alternative embodiment of anexpandable fusion device shown in an unexpanded position in accordancewith one embodiment of the present invention;

FIG. 19 is a front perspective view of the expandable fusion device ofFIG. 18 shown in an expanded position in accordance with one embodimentof the present invention;

FIG. 20 is a rear perspective view of the expandable fusion device ofFIG. 18 shown in an unexpanded position in accordance with oneembodiment of the present invention;

FIG. 21 is a rear perspective view of the expandable fusion device ofFIG. 18 shown in an expanded position in accordance with one embodimentof the present invention;

FIG. 22 is a side view of the expandable fusion device of FIG. 18 shownin an unexpanded position in accordance with one embodiment of thepresent invention;

FIG. 23 is a side view of the expandable fusion device of FIG. 18 shownin an expanded position in accordance with one embodiment of the presentinvention;

FIG. 24 is a perspective of an endplate of the expandable fusion deviceof FIG. 18 in accordance with one embodiment of the present invention;

FIG. 25 is a perspective view of the central ramp of the expandablefusion device of FIG. 18 in accordance with one embodiment of thepresent invention;

FIG. 26 is a side view of the central ramp of the expandable fusiondevice of FIG. 18 in accordance with one embodiment of the presentinvention;

FIG. 27 is a top view of the central ramp of the expandable fusiondevice of FIG. 18 in accordance with one embodiment of the presentinvention;

FIG. 28 a perspective view showing placement of the central ramp of theexpandable fusion device of FIG. 18 in accordance with one embodiment ofthe present invention;

FIG. 29 is a perspective view showing placement of the first endplate ofthe expandable fusion device of FIG. 18 in accordance with oneembodiment of the present invention;

FIG. 30 is a perspective view showing placement of the second endplateof the expandable fusion device of FIG. 18 in accordance with oneembodiment of the present invention;

FIG. 31 is a perspective view showing placement of the actuation memberof the expandable fusion device of FIG. 18 in accordance with oneembodiment of the present invention;

FIG. 32 is a perspective view showing expansion of the expandable fusiondevice of FIG. 18 in accordance with one embodiment of the presentinvention;

FIG. 33 is a front perspective view of an alternative embodiment of anexpandable fusion device shown in an unexpanded position in accordancewith one embodiment of the present invention;

FIG. 34 is a front perspective view of the expandable fusion device ofFIG. 33 shown in an expanded position in accordance with one embodimentof the present invention;

FIG. 35 is a rear perspective view of the expandable fusion device ofFIG. 33 shown in an unexpanded position in accordance with oneembodiment of the present invention;

FIG. 36 is a rear perspective view of the expandable fusion device ofFIG. 33 shown in an expanded position in accordance with one embodimentof the present invention;

FIG. 37 is a side cross-sectional view of the expandable fusion deviceof FIG. 33 shown in an unexpanded position in accordance with oneembodiment of the present invention;

FIG. 38 is a side cross-sectional view of the expandable fusion deviceof FIG. 33 shown in an expanded position in accordance with oneembodiment of the present invention;

FIG. 39 is a perspective of an endplate of the expandable fusion deviceof FIG. 33 in accordance with one embodiment of the present invention;

FIG. 40 is a rear perspective view of an alternative embodiment of anexpandable fusion device shown in an unexpanded position in accordancewith one embodiment of the present invention;

FIG. 41 is a rear perspective view of the expandable fusion device ofFIG. 40 shown in a partially expanded position in accordance with oneembodiment of the present invention;

FIG. 42 is a rear perspective view of the expandable fusion device ofFIG. 40 shown in an expanded position in accordance with one embodimentof the present invention;

FIG. 43 is a side exploded view of the expandable fusion device of FIG.40 in accordance with one embodiment of the present invention;

FIG. 44 is a side cross-sectional view of the expandable fusion deviceof FIG. 40 shown in an unexpanded position in accordance with oneembodiment of the present invention;

FIG. 45 is a perspective view of an endplate of the expandable fusiondevice of FIG. 40 in accordance with one embodiment of the presentinvention;

FIG. 46 is a perspective view of the central ramp of the expandablefusion device of FIG. 40 in accordance with one embodiment of thepresent invention;

FIGS. 47-49 are perspective views of the driving ramp of the expandablefusion device of FIG. 40 in accordance with one embodiment of thepresent invention;

FIG. 50 is a rear perspective view of an alternative embodiment of anexpandable fusion device shown in an expanded position in accordancewith one embodiment of the present invention;

FIG. 51 is a side cross-sectional view of the expandable fusion deviceof FIG. 50 shown in an expanded position in accordance with oneembodiment of the present invention;

FIG. 52 is an exploded view of the expandable fusion device of FIG. 50in accordance with one embodiment of the present invention;

FIG. 53 is a top view of the expandable fusion device of FIG. 50 shownin an unexpanded position in accordance with one embodiment of thepresent invention;

FIG. 54 is a read end view of the expandable fusion device of FIG. 50shown in an expanded position in accordance with one embodiment of thepresent invention;

FIG. 55 is a perspective view of an endplate of the expandable fusiondevice of FIG. 50 in accordance with one embodiment of the presentinvention;

FIG. 56 is a perspective of a central ramp of the expandable fusiondevice of FIG. 50 in accordance with one embodiment of the presentinvention; and

FIG. 57 is a perspective view of a driving ramp of the expandable fusiondevice of FIG. 50 in accordance with one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiment(s) is merelyexemplary in nature and is in no way intended to limit the invention,its application, or uses.

A spinal fusion is typically employed to eliminate pain caused by themotion of degenerated disk material. Upon successful fusion, a fusiondevice becomes permanently fixed within the intervertebral disc space.Looking at FIG. 1, an exemplary embodiment of an expandable fusiondevice 10 is shown between adjacent vertebral bodies 2 and 3. The fusiondevice 10 engages the endplates 4 and 5 of the adjacent vertebral bodies2 and 3 and, in the installed position, maintains normal intervertebraldisc spacing and restores spinal stability, thereby facilitating anintervertebral fusion. The expandable fusion device 10 can bemanufactured from a number of materials including titanium, stainlesssteel, titanium alloys, non-titanium metallic alloys, polymericmaterials, plastics, plastic composites, PEEK, ceramic, and elasticmaterials. In an embodiment, the expandable fusion device 10 can beconfigured to be placed down an endoscopic tube and into the disc spacebetween the adjacent vertebral bodies 2 and 3.

In an exemplary embodiment, bone graft or similar bone growth inducingmaterial can be introduced around and within the fusion device 10 tofurther promote and facilitate the intervertebral fusion. The fusiondevice 10, in one embodiment, is preferably packed with bone graft orsimilar bone growth inducing material to promote the growth of bonethrough and around the fusion device. Such bone graft may be packedbetween the endplates of the adjacent vertebral bodies prior to,subsequent to, or during implantation of the fusion device.

With reference to FIGS. 2-7, an embodiment of the fusion device 10 isshown. In an exemplary embodiment, the fusion device 10 includes a firstendplate 14, a second endplate 16, a central ramp 18, and a driving ramp260. In an embodiment, the expandable fusion device 10 can be configuredto be placed down an endoscopic tube and into the disc space between theadjacent vertebral bodies 2 and 3. One or more components of the fusiondevice 10 may contain features, such as through bores, that facilitateplacement down an endoscopic tube. In an embodiment, components of thefusion device 10 are placed down the endoscopic tube with assembly ofthe fusion device 10 in the disc space.

Although the following discussion relates to the second endplate 16, itshould be understood that it also equally applies to the first endplate14 as the second endplate 16 is substantially identical to the firstendplate 14 in embodiments of the present invention. Turning now toFIGS. 2-7 and 10, in an exemplary embodiment, the second endplate 16 hasa first end 39 and a second end 41. In the illustrated embodiment, thesecond endplate 16 further comprise an upper surface 40 connecting thefirst end 39 and the second end 41, and a lower surface 42 connectingthe first end 39 and the second end 41. In an embodiment, the secondendplate 16 further comprises a through opening 44, as seen on FIG. 11.The through opening 44, in an exemplary embodiment, is sized to receivebone graft or similar bone growth inducing material and further allowthe bone graft or similar bone growth inducing material to be packed inthe central opening in the central ramp 18.

As best seen in FIGS. 7 and 10, the lower surface 42 includes at leastone extension 46 extending along at least a portion of the lower surface42, in an embodiment. In an exemplary embodiment, the extension 46 canextend along a substantial portion of the lower surface 42, including,along the center of the lower surface 42. In the illustrated embodiment,the extension 46 includes a generally concave surface 47. The concavesurface 47 can form a through bore with the corresponding concavesurface 47 (not illustrated) of the first endplate 14, for example, whenthe device 10 is in an unexpanded configuration. In another exemplaryembodiment, the extension 46 includes at least one ramped surface 48. Inanother exemplary embodiment, there are two ramped surfaces 48, 50 withthe first ramped surface 48 facing the first end 39 and the secondramped surface facing the second end 41. In an embodiment, the firstramped surface 48 can be proximate the first end 39, and the secondramped surface 50 can be proximate the second end 41. It is contemplatedthat the slope of the ramped surfaces 48, 50 can be equal or can differfrom each other. The effect of varying the slopes of the ramped surfaces48, 50 is discussed below.

In one embodiment, the extension 46 can include features for securingthe endplate 16 when the expandable fusion device 10 is in an expandedposition. In an embodiment, the extension 46 includes one or moreprotuberances 49 extending from the lateral sides 51 of the extension.In the illustrated embodiment, there are two protuberances 49 extendingfrom each of the lateral sides 51 with each of the sides 53 having oneof the protuberances 49 extending from a lower portion of either end. Aswill be discussed in more detail below, the protuberances 49 can befigured to engage the central ramp 18 preventing and/or restrictinglongitudinal movement of the endplate 16 when the device 10 is in anexpanded position.

As illustrated in FIGS. 2-5, in one embodiment, the upper surface 40 ofthe second endplate 16 is flat and generally planar to allow the uppersurface 40 of the endplate 16 to engage with the adjacent vertebral body2. Alternatively, as shown in FIG. 15, the upper surface 40 can becurved convexly or concavely to allow for a greater or lesser degree ofengagement with the adjacent vertebral body 2. It is also contemplatedthat the upper surface 40 can be generally planar but includes agenerally straight ramped surface or a curved ramped surface. The rampedsurface allows for engagement with the adjacent vertebral body 2 in alordotic fashion. While not illustrated, in an exemplary embodiment, theupper surface 40 includes texturing to aid in gripping the adjacentvertebral bodies. Although not limited to the following, the texturingcan include teeth, ridges, friction increasing elements, keels, orgripping or purchasing projections.

Referring now to FIGS. 2-8, in an exemplary embodiment, the central ramp18 has a first end 20, a second end 22, a first side portion 24connecting the first end 20 and the second end 22, and a second sideportion 26 (best seen on FIG. 5) on the opposing side of the centralramp 12 connecting the first end 20 and the second end 22. The firstside portion 24 and the second side portion 26 may be curved, in anexemplary embodiment. The central ramp 18 further includes a lower end28, which is sized to receive at least a portion of the first endplate14, and an upper end 30, which is sized to receive at least a portion ofthe second endplate 16.

The first end 20 of the central ramp 18, in an exemplary embodiment,includes an opening 32. The opening 32 can be configured to receive anendoscopic tube in accordance with one or more embodiments. The firstend 20 of the central ramp 18, in an exemplary embodiment, includes atleast one angled surface 33, but can include multiple angled surfaces.The angled surface 33 can serve to distract the adjacent vertebralbodies when the fusion device 10 is inserted into an intervertebralspace.

The second end 22 of the central ramp 18, in an exemplary embodiment,includes an opening 36. The opening 36 extends from the second end 22 ofthe central ramp 18 into a central guide 37 in the central ramp 18.

In an embodiment, the central ramp 18 further includes one or moreramped surfaces 33. As best seen in FIG. 8, the one or more rampedsurfaces 33 positioned between the first side portion 24 and the secondside portion 26 and between the central guide 37 and the second end 22.In an embodiment, the one or more ramped surfaces 33 face the second end22 of the central ramp 18. In one embodiment, the central ramp 18includes two ramped surfaces 33 with one of the ramped surfaces 33 beingsloped upwardly and the other of the ramped surfaces 33 being slopeddownwardly. The ramped surfaces 33 of the central ramp can be configuredand dimensioned to engage the ramped surface 48 in each of the first andsecond endplates 14, 16.

Although the following discussion relates to the second side portion 26of the central ramp 18, it should be understood that it also equallyapplies to the first side portion 24 in embodiments of the presentinvention. In the illustrated embodiment, the second side portion 26includes an inner surface 27. In an embodiment, the second side portion26 further includes a lower guide 35, a central guide 37, and an upperguide 38. In the illustrated embodiment, the lower guide 35, centralguide 37, and the upper guide 38 extend out from the inner surface 27from the second end 22 to the one or more ramped surfaces 31. In theillustrated embodiment, the second end 22 of the central ramp 18 furtherincludes one or more guides 38. The guides 38 can serve to guide thetranslational movement of the first and second endplates 14, 16 withrespect to the central ramp 18. For example, protuberances 49 on thesecond endplate 16 may be sized to be received between the central guide37 and the upper guide 38. Protuberances 49 of the first endplate 16 maybe sized to be received between the central guide 37 and the lower guide35. A first slot 29 may be formed proximate the middle of the upperguide 38. A second slot 31 may be formed between end of the upper guide38 and the one or more ramped surfaces 33. The protuberances 49 may besized to be received within the first slot 29 and/or the second slot 31when the device 10 is in the expanded position.

Referring now to FIGS. 4-7 and 9, the driving ramp 260 has a throughbore 262. In an embodiment, the driving ramp 260 is generallywedge-shaped. As illustrated, the driving ramp 260 may comprise a wideend 56, a narrow end 58, a first side portion 60 connecting the wide end56 and the narrow end 58, and a second side portion 62 connecting thewide end 56 and the narrow end 58. The driving ramp 260 further maycomprise ramped surfaces, including an upper ramped surface 64 and anopposing lower ramped surface 66. The upper ramped surface 64 and thelower ramped surface 66 may be configured and dimensioned to engage theramped surface 50 proximate the second end 41 in of the first and thesecond endplates 14, 16. The first and second side portions 60, 62 mayeach include grooves 68 that extend, for example, in a directionparallel to the longitudinal axis of the through bore 262. The grooves68 may be sized to receive the central guide 37 on the interior surface27 of each of the side portions 24, 26 of the central ramp 18. In thismanner, the grooves 68 together with the central guide 37 can surface toguide the translational movement of the driving ramp 260 in the centralramp 18.

A method of installing the expandable fusion device 10 of FIG. 1 is nowdiscussed in accordance with one embodiment of the present invention.Prior to insertion of the fusion device 10, the intervertebral space isprepared. In one method of installation, a discectomy is performed wherethe intervertebral disc, in its entirety, is removed. Alternatively,only a portion of the intervertebral disc can be removed. The endplatesof the adjacent vertebral bodies 2, 3 are then scraped to create anexposed end surface for facilitating bone growth across theintervertebral space. One or more endoscopic tubes can then be insertedinto the disc space. The expandable fusion device 10 can then beintroduced into the intervertebral space down an endoscopic tube andseated in an appropriate position in the intervertebral disc space.

After the fusion device 10 has been inserted into the appropriateposition in the intervertebral disc space, the fusion device 10 can thenbe expanded into the expanded position. To expand the fusion device 10,the driving ramp 260 may moved in a first direction with respect to thecentral ramp 18. Translational movement of the driving ramp 260 throughthe central ramp 18 may be guided by the central guide 37 on each of thefirst and second side portions 24, 26 of the central ramp 18. As thedriving ramp 260 moves, the upper ramped surface 64 pushes against theramped surface 50 proximate the second end 41 of the second endplate 16,and the lower ramped surface 66 pushes against the ramped surface 50proximate the second end 41 of the first endplate 14. In addition, theramped surfaces 33 in the central ramp 18 push against the rampedsurface 48 proximate the first end 41 of the first and second endplates14, 16. In this manner, the first and second endplates 14, 16 are pushedoutwardly into an expanded configuration. As discussed above, thecentral ramp 16 includes locking features for securing the endplates 14,16.

It should also be noted that the expansion of the endplates 14, 16 canbe varied based on the differences in the dimensions of the rampedsurfaces 48, 50 and the angled surfaces 62, 64. As best seen in FIG. 16,the endplates 14, 16 can be expanded in any of the following ways:straight rise expansion, straight rise expansion followed by a toggleinto a lordotic expanded configuration, or a phase off straight riseinto a lordotic expanded configuration.

Turning back to FIGS. 2-7, in the event the fusion device 10 needs to berepositioned or revised after being installed and expanded, the fusiondevice 10 can be contracted back to the unexpanded configuration,repositioned, and expanded again once the desired positioning isachieved. To contract the fusion device 10, the central ramp 18 is movedwith respect to the central ramp 260 away from the central ramp 260. Asthe central ramp 18 moves, the ramped surfaces 33 in the central ramp 18ride along the ramped surfaces 48 of the first and second endplates 14,16 with the endplates 14, 16 moving inwardly into the unexpandedposition.

With reference now to FIG. 17, fusion device 10 is shown with anexemplary embodiment of artificial endplates 100. Artificial endplates100 allows the introduction of lordosis even when the endplates 14 and16 of the fusion device 10 are generally planar. In one embodiment, theartificial endplates 100 have an upper surface 102 and a lower surface104. The upper surfaces 102 of the artificial endplates 100 have atleast one spike 106 to engage the adjacent vertebral bodies. The lowersurfaces 104 have complementary texturing or engagement features ontheir surfaces to engage with the texturing or engagement features onthe upper endplate 14 and the lower endplate 16 of the fusion device 10.In an exemplary embodiment, the upper surface 102 of the artificialendplates 100 have a generally convex profile and the lower surfaces 104have a generally parallel profile to achieve lordosis. In anotherexemplary embodiment, fusion device 10 can be used with only oneartificial endplate 100 to introduce lordosis even when the endplates 14and 16 of the fusion device 10 are generally planar. The artificialendplate 100 can either engage endplate 14 or engage endplate 16 andfunction in the same manner as described above with respect to twoartificial endplates 100.

With reference to FIGS. 11-14, an embodiment for placing an expandablefusion device 10 into an intervertebral disc space is illustrated. Theexpandable fusion device 10 can be introduced into the intervertebralspace down an endoscopic tube utilizing a tool 70 that is attached toendplate 16, with the second endplate 16 being first placed down thetube with tool 70 and into the disc space, as seen in FIG. 11. Afterinsertion of the second endplate 16, the first endplate 14 can be placeddown the same endoscopic tube with tool 72 and into the disc space, asshown on FIG. 12. Following the first endplate 14, the central ramp 12can be placed down the same endoscopic tube and into the disc spaceguided by tools 70 and 72, as shown on FIGS. 13 and 14.

Referring now to FIGS. 18-23, an alternative embodiment of theexpandable fusion device 10 is shown. In an exemplary embodiment, thefusion device 10 includes a first endplate 14, a second endplate 16, acentral ramp 18, and an actuator assembly 200. As will be discussed inmore detail below, the actuator assembly 200 drives the central ramp 18which forces apart the first and second endplates 14, 16 to place theexpandable fusion device in an expanded position. One or more componentsof the fusion device 10 may contain features, such as through bores,that facilitate placement down an endoscopic tube. In an embodiment,components of the fusion device 10 are placed down the endoscopic tubewith assembly of the fusion device 10 in the disc space.

Although the following discussion relates to the second endplate 16, itshould be understood that it also equally applies to the first endplate14 as the second endplate 16 is substantially identical to the firstendplate 14 in embodiments of the present invention. With additionalreference to FIG. 24, in an exemplary embodiment, the second endplate 16has a first end 39 and a second end 41. In the illustrated embodiment,the second endplate 16 further comprise an upper surface 40 connectingthe first end 39 and the second end 41, and a lower surface 42connecting the first end 39 and the second end 41. While notillustrated, in an embodiment, the second endplate 16 further comprisesa through opening. The through opening, in an exemplary embodiment, issized to receive bone graft or similar bone growth inducing material.

In one embodiment, the upper surface 40 of the second endplate 16 isflat and generally planar to allow the upper surface 40 of the endplate16 to engage with the adjacent vertebral body 2. Alternatively, as shownin FIG. 15, the upper surface 40 can be curved convexly or concavely toallow for a greater or lesser degree of engagement with the adjacentvertebral body 2. It is also contemplated that the upper surface 40 canbe generally planar but includes a generally straight ramped surface ora curved ramped surface. The ramped surface allows for engagement withthe adjacent vertebral body 2 in a lordotic fashion. While notillustrated, in an exemplary embodiment, the upper surface 40 includestexturing to aid in gripping the adjacent vertebral bodies. Although notlimited to the following, the texturing can include teeth, ridges,friction increasing elements, keels, or gripping or purchasingprojections.

In one embodiment, the second endplate 16 further comprises a first sideportion 202 connecting the first end 39 and the second end 41, and asecond side portion 204 connecting the first end 39 and the second end41. In the illustrated embodiment, the first and second side portions202, 204 are extensions from the lower surface 42. In an exemplaryembodiment, the first and second side portions 202, 204 each includeramped surfaces 206, 208. In the illustrated embodiment, the rampedsurfaces 206, 208 extend from the first end 39 of the second endplate 16to bottom surfaces 210, 212 of each of the side portions 202, 204. Inone embodiment, the ramped surfaces 206, 208 are forward facing in thatthe ramped surfaces 206, 208 face the first end 39 of the secondendplate. As previously discussed, the slope of the ramped surfaces 206,208 may be varied as desired for a particular application.

In an embodiment, the first and second side portions 202, 204 eachcomprise at least one protuberance 214. In an exemplary embodiment, thefirst and second side portions 202, 204 each comprise a firstprotuberance 214, a second protuberance 216, and a third protuberance218. In one embodiment, the protuberances 214, 216, 218 extend from theinterior surface 220 of the first and second side portions 202, 204. Inan exemplary embodiment, the protuberances 214, 216, 218 extend at thelower side of the interior surface 220. As best seen in FIG. 24, thefirst and the second protuberances 214, 216 form a first slot 222, andthe second and third protuberances 216, 218 form a second slot 224.

As best seen in FIG. 24, the lower surface 42 of the second endplate 16,in an embodiment, includes a central extension 224 extending along atleast a portion of the lower surface. In the illustrated embodiment, thecentral extension 224 extends between the first and second side portions202 and 204. In an exemplary embodiment, the central extension 224 canextend from the second end 41 of the endplate 16 to the central portionof the endplate. In one embodiment, the central extension 224 includes agenerally concave surface 226 configured and dimensioned to form athrough bore with the corresponding concave surface 226 (notillustrated) of the first endplate 14. The central extension 224 canfurther include, in an exemplary embodiment, a ramped surface 228. Inthe illustrated embodiment, the ramped surface 228 faces the first end39 of the endplate 16. The ramped surface 228 can be at one end of thecentral extension 224. In an embodiment, the other end of the centralextension 224 forms a stop 230. In the illustrated embodiment, the stop230 is recessed from the second end 41 of the second endplate 16.

Referring to FIGS. 25-27, in an exemplary embodiment, the central ramp18 includes a body portion 232 having a first end 234 and a second end236. In an embodiment, the body portion 232 includes at least a firstexpansion portion 238. In an exemplary embodiment, the body portion 232includes a first expansion portion 238 and a second expansion portion240 extending from opposing sides of the body portion with each of thefirst and second expansion portions 238, 240 having a generallytriangular cross-section. In one embodiment, the expansion portions 238,240 each have angled surfaces 242, 244 configured and dimensioned toengage the ramped surfaces 206, 208 of the first and second endplates14, 16 and force apart the first and second endplates 14, 16. In anembodiment, the engagement between the angled surfaces 242, 244 of theexpansion portions 238, 240 with the ramped surfaces 206, 208 of thefirst and second endplates 14, 16 may be described as a dovetailconnection.

The second end 236 of the central ramp 18, in an exemplary embodiment,includes opposing angled surfaces 246. The angled surfaces 246 can beconfigured and dimensioned to engage the ramped surface 228 in thecentral extension 224 in each of the first and second endplates 14, 16.In other words, one of the angled surfaces 246 can be upwardly facingand configured, in one embodiment, to engage the ramped surface 228 inthe central extension 224 in the second endplate 16. In an embodiment,the engagement between the angled surfaces 246 of the second end 236 ofthe central ramp 18 with the ramped surface 228 in the first and secondendplates 14, 16 may be described as a dovetail connection.

The second end 236, in an exemplary embodiment, can further include anextension 252. In the illustrated embodiment, the extension 252 isgenerally cylindrical in shape with a through bore 254 extendinglongitudinally therethrough. In one embodiment, the extension 252 caninclude a beveled end 256. While not illustrated, at least a portion ofthe extension 252 can be threaded.

Referring still to FIGS. 25-27, the central ramp 18 can further includefeatures for securing the first and second endplates 14, 16 when theexpandable fusion device 10 is in an expanded position. In anembodiment, the body portion 232 of the central ramp 18 includes one ormore protuberances 248, 250 extending from opposing sides of the bodyportion 232. As illustrated, the protuberances 248, 250, in oneembodiment, can be spaced along the body portion 232. In an exemplaryembodiment, the protuberances 248, 250 can be configured and dimensionedfor insertion into the corresponding slots 222, 224 in the first andsecond endplates 14, 16 when the device 10 is in an expanded position,as best seen in FIGS. 19 and 21. The protuberances 248, 250 can engagethe endplates 14, 16 preventing and/or restricting movement of theendplates 14, 16 with respect to the central ramp 18 after expansion ofthe device 10.

With reference to FIGS. 20-23, in an exemplary embodiment, the actuatorassembly 200 has a flanged end 253 configured and dimensioned to engagethe stop 232 in the central extension 224 of the first and the secondendplates 14, 16. In an embodiment, the actuator assembly 200 furtherincludes an extension 254 that extends from the flanged end 253. In afurther embodiment, the actuator assembly 200 includes a threaded hole256 that extends through the actuator assembly 200. It should beunderstood that, while the threaded hole 256 in the actuator assembly200 is referred to as threaded, the threaded hole 256 may only bepartially threaded in accordance with one embodiment. In an exemplaryembodiment, the threaded hole 256 is configured and dimensioned tothreadingly receive the extension 252 of the central ramp 18.

With additional reference to FIGS. 28-32, a method of installing theexpandable fusion device 10 of FIGS. 18-27 is now discussed inaccordance with one embodiment of the present invention. Prior toinsertion of the fusion device, the disc space may be prepared asdescribed above and then one or more endoscopic tubes may then insertedinto the disc space. The expandable fusion device 10 can then beinserted into and seated in the appropriate position in theintervertebral disc space, as best seen in FIGS. 28-32. The expandablefusion device 10 can be introduced into the intervertebral space down anendoscopic tube (not illustrated), with the central ramp 18 being firstplaced down the tube and into the disc space, as seen in FIG. 28. Afterinsertion of the central ramp, the first endplate 14 can be placed downan endoscopic tube, as shown on FIG. 29, followed by insertion of thesecond endplate 16, as shown on FIG. 30. After the second endplate 16,the actuator assembly 200 can then be inserted to complete assembly ofthe device 10, as best seen in FIG. 31.

After the fusion device 10 has been inserted into and assembled in theappropriate position in the intervertebral disc space, the fusion device10 can then be expanded into the expanded position. To expand the fusiondevice 10, the actuator assembly 200 can be rotated. As discussed above,the actuator assembly 200 is in threaded engagement with the extension250 of the central ramp 18. Thus, as the actuator assembly 200 isrotated in a first direction, the central ramp 18 moves toward theflanged end 253 of the actuator assembly 200. In another exemplaryembodiment, the actuator assembly 200 can be moved in a linear directionwith the ratchet teeth as means for controlling the movement of thecentral ramp 18. As the central ramp 18 moves, the angled surfaces 242,244 in the expansion portions 238, 240 of the central ramp 18 pushagainst the ramped surfaces 206, 208 in the first and second sideportions 202, 204 of the first and second endplates 14, 16. In addition,the angled surfaces 246 in the second end 236 of the central ramp 18also push against the ramped surfaces 228 in the central extension 224of each of the endplates 14, 16. This is best seen in FIGS. 22-23.

Since the expansion of the fusion device 10 is actuated by a rotationalinput, the expansion of the fusion device 10 is infinite. In otherwords, the endplates 14, 16 can be expanded to an infinite number ofheights dependent on the rotational advancement of the actuator assembly200. As discussed above, the central ramp 16 includes locking featuresfor securing the endplates 14, 16.

In the event the fusion device 10 needs to be repositioned or revisedafter being installed and expanded, the fusion device 10 can becontracted back to the unexpanded configuration, repositioned, andexpanded again once the desired positioning is achieved. To contract thefusion device 10, the actuator assembly 200 can be rotated in a seconddirection. As discussed above, actuator assembly 200 is in threadedengagement with the extension 250 of the central ramp 18; thus, as theactuator assembly 200 is rotated in a second direction, opposite thefirst direction, the central ramp 18 moves with respect to the actuatorassembly 200 and the first and second endplates 14, 16 away from theflanged end 253. As the central ramp 18 moves, the first and secondendplates are pulled inwardly into the unexpanded position.

Referring now to FIGS. 33-38, an alternative embodiment of theexpandable fusion device 10 is shown. In the illustrated embodiment, thefusion device includes a first endplate 14, a second endplate 16, acentral ramp 18, and an actuator assembly 200. The fusion device 10 ofFIGS. 33-38 and its individual components are similar to the device 10illustrated on FIGS. 18-23 with several modifications. The modificationsto the device 10 will be described in turn below.

Although the following discussion relates to the second endplate 16, itshould be understood that it also equally applies to the first endplate14 as the second endplate 16 is substantially identical to the firstendplate 14 in embodiments of the present invention. With additionalreference to FIG. 39, in an exemplary embodiment, the lower surface 42of the second endplate 16 has been modified. In one embodiment, thecentral extension 224 extending from the lower surface 42 has beenmodified to include a second ramped surface 258 rather than a stop. Inan exemplary embodiment, the second ramped surface 258 faces the secondend 41 of the second endplate 16. In contrast, ramped surface 228 on thecentral extension 228 faces the first end 39 of the second endplate. Theconcave surface 228 connects the ramped surface 228 and the secondramped surface 258.

With reference to FIGS. 35-38, in an exemplary embodiment, the actuatorassembly 200 has been modified to further include a driving ramp 260. Inthe illustrated embodiment, the driving ramp 260 has a through bore 262through which the extension 254 extends. In an embodiment, the drivingramp 260 is generally wedge-shaped. As illustrated, the driving ramp 260may comprise a blunt end 264 in engagement with the flanged end 253. Inan exemplary embodiment, the driving ramp 260 further comprises angledsurfaces 266 configured and dimensioned to engage the second rampedsurface 258 of each of the endplates 14, 16 and force apart the firstand second endplates 14, 16.

Referring now to FIGS. 40-44, an alternative embodiment of theexpandable fusion device 10 is shown. In the illustrated embodiment, thefusion device 10 includes a first endplate 14, a second endplate 16, acentral ramp 18, an actuator assembly 200, and a driving ramp 300. Aswill be discussed in more detail below, the actuator assembly 200functions, in an embodiment, to pull the central ramp 18 and the drivingramp 300 together, which forces apart the first and second endplates 14,16. In an embodiment, the expandable fusion device

Although the following discussion relates to the first endplate 14, itshould be understood that it also equally applies to the second endplate16 as the second endplate 16 is substantially identical to the firstendplate 14 in embodiments of the present invention. With reference toFIGS. 40-45, in an exemplary embodiment, the first endplate 14 has afirst end 39 and a second end 41. In the illustrated embodiment, thefirst endplate 14 further comprises an upper surface 40 connecting thefirst end 39 and the second end 41, and a lower surface 42 connectingthe first end 39 and the second end 41. While not illustrated, in anembodiment, the first endplate 14 may comprise further comprises athrough opening. The through opening, in an exemplary embodiment, issized to receive bone graft or similar bone growth inducing material.

In one embodiment, the upper surface 40 of the first endplate 14 is flatand generally planar to allow the upper surface 40 of the endplate 14 toengage with the adjacent vertebral body 2. Alternatively, as shown inFIG. 15, the upper surface 40 can be curved convexly or concavely toallow for a greater or lesser degree of engagement with the adjacentvertebral body 2. It is also contemplated that the upper surface 40 canbe generally planar but includes a generally straight ramped surface ora curved ramped surface. The ramped surface allows for engagement withthe adjacent vertebral body 2 in a lordotic fashion. While notillustrated, in an exemplary embodiment, the upper surface 40 includestexturing to aid in gripping the adjacent vertebral bodies. Although notlimited to the following, the texturing can include teeth, ridges,friction increasing elements, keels, or gripping or purchasingprojections.

In one embodiment, the first endplate 14 further comprises a first sideportion 202 connecting the first end 39 and the second end 41, and asecond side portion 204 connecting the first end 39 and the second end41. In the illustrated embodiment, the first and second side portions202, 204 are extensions from the lower surface 42. In an embodiment, thefirst and second side portions each have an interior surface 302 and anexterior surface 304. In an exemplary embodiment, the first and secondside portions 202, 204 each include one or more ramped portions. In theillustrated embodiment, the first and second side portions 202, 204include first ramped portions 306, 308 at the first end 39 of theendplate 14 and second ramped portions 310, 312 at the second end 41 ofthe endplate. The first and second side portions 202, 204 each caninclude a bridge portion 314 connecting the first ramped portions 306,308 and the second ramped portions 310, 312. In an embodiment, the firstramped portions 306, 308 abut the exterior surface 304 of the respectiveside portions 202, 204, and the second ramped portions 310, 312 abut theinterior surface 302 of the respective side portions 202, 204. Asillustrated, the first ramped portions 306, 308 may include tongueportions 316, 318 with the tongue portions 316, 318 extending in anoblique direction with respect to the upper surface 40 of the endplate14. As further illustrated, the second ramped portions 310, 312 mayinclude tongue portions 320, 322 that extend in an oblique directionwith respect to the upper surface 40 of the endplate 14.

As best seen in FIG. 45, the lower surface 42 of the second endplate 16,in an embodiment, includes a central extension 224 extending along atleast a portion of the lower surface. In the illustrated embodiment, thecentral extension 224 extends between the first and second side portions202 and 204. In an exemplary embodiment, the central extension 224 canextend generally between the first ramped portions 306, 308 and thesecond ramped portions 310, 312. In one embodiment, the centralextension 224 includes a generally concave surface 226 configured anddimensioned to form a through bore with the corresponding concavesurface 226 (not illustrated) of the second endplate 16.

With reference to FIGS. 43 and 44, the actuator assembly 200 includes ahead portion 324, a rod receiving extension 326, and a connectingportion 328 that connecting portions that connects the head portion 324and the rod receiving extension 326. As illustrated, the head portion324 may include one or more instrument gripping features 330 that canallow it to be turned by a suitable instrument. In addition, the headportion 324 has a larger diameter than the other components of theactuator assembly 200 to provide a contact surface with the driving ramp300. In the illustrated embodiment, the head portion 324 includes a rim332 that provides a surface for contacting the driving ramp 300. As canbe seen in FIG. 44, in an exemplary embodiment, the rod receivingextension 326 includes an opening sized and dimensioned to receive theextension 336 of the central ramp 18. In an embodiment, the rodreceiving extension 326 includes threading for threadingly engaging theextension 336. In another embodiment, the rod receiving extension 326includes ratchet teeth for engaging the extension 336. In theillustrated embodiment, the head portion 324 and the rod receivingextension 326 are connected by connecting portion 328 which can begenerally cylindrical in shape.

With reference to FIGS. 43, 44, and 46, the central ramp 18 includesexpansion portion 334 and extension 336. As best seen in FIG. 46, theexpansion portion 334 may include an upper portion 338 and side portions340, 342 that extend down from the upper portion 338. In an embodiment,each of the side portions 340, 342 include dual, overlapping rampedportions. For example, side portions 340, 342 each include a firstramped portion 344 that overlaps a second ramped portion 346. In theillustrated embodiment, the first ramped portion 344 faces the extension336 while the second ramped portion 344 faces away from the extension336. In one embodiment, angled grooves 348, 350 are formed in each ofthe first and second ramped portions 344, 346. In another embodiment,the angled grooves 348, 350 are sized to receive the correspondingtongues 316, 318, 320, 322 in the first and second endplates with angledgrooves 348 receiving tongues 320, 322 in the second endplate 16 andangled grooves 350 receiving tongues 316, 318 in the first endplate 14.Although the device 10 is described with tongues 316, 318, 320, 322 onthe endplates 14, 16 and angled grooves 348, 350 on the central ramp 18,it should be understood that that device 10 can also be configured withgrooves on the endplates 14, 16 and tongues on the central ramp 18, inaccordance with one embodiment of the present invention.

In an exemplary embodiment, the extension 336 is sized to be receivedwithin the rod receiving extension 326 of the actuator assembly 200. Inone embodiment, the extension 336 has threading with the extension 336being threadingly received within the rod receiving extension 326. Inanother embodiment, the extension 336 has ratchet teeth with theextension 336 being ratcheted into the rod receiving extension 336. Inan embodiment, the extension 336 include nose 352 at the end of theextension 336.

With reference to FIGS. 47-49, in an exemplary embodiment, the drivingramp 300 includes an upper portion 354 having an upper surface 356 andan oblique surface 358. In an embodiment, the driving ramp 300 furtherincludes side portions 360, 362 that extend from the upper portion 354connecting the upper portion 354 with the lower portion 364 of thedriving ramp 300. As best seen in FIGS. 48-49, the driving ramp 300further includes a bore 366, in an exemplary embodiment, sized toreceive the connection portion 328 of the actuator assembly 200. In oneembodiment, the driving ramp 300 moves along the connection portion 328when the actuator assembly 200 is pushing the driving ramp 300. In anexemplary embodiment, the driving ramp 300 further includes contactsurface 368 that engages the rim 332 of the head portion 324 of theactuator assembly 200. In the illustrated embodiment, the contactsurface 368 has a generally annular shape.

In an exemplary embodiment, the side portions 360, 362 of the drivingramp 300 each include overlapping ramped portions. For example, the sideportions 360, 362 each include first ramped portions 370 that overlapsecond ramped portions 372. In the illustrated embodiment, the firstramped portions 370 face central ramp 18 while the second rampedportions 372 face the opposite direction. In one embodiment, angledgrooves 374, 376 are formed in each of the first and second rampedportions 370, 372. FIG. 48 is a perspective view of the driving ramp 300that shows the top ends of the angled grooves 374 in ramped portions370. FIG. 49 is a perspective view of the driving ramp 300 that showsthe top ends of the angled grooves 376 in ramped portions 372. In anexemplary embodiment, the angled grooves 374, 376 are sized to receivecorresponding tongues 316, 318, 320, 322 in the first and secondendplates 14, 16 with angled grooves 370 receiving tongues 316, 318 inthe second endplate 16 and angled grooves 372 receiving tongues 320, 322in the first endplate 14. Although the device 10 is described withtongues 316, 318, 320, 322 in the first and second endplates 14, 16 andangled grooves 370, 372, 374, 376 on the driving ramp 300, it should beunderstood that that device 10 can also be configured with grooves onthe second endplate 16 and tongues on the driving ramp 300, inaccordance with one embodiment of the present invention.

Turning now to FIGS. 40-42, a method of installing the expandable fusiondevice 10 of FIGS. 40-49 is now discussed in accordance with oneembodiment of the present invention. Prior to insertion of the fusiondevice, the disc space may be prepared as described above. Theexpandable fusion device 10 can then be inserted into and seated in theappropriate position in the intervertebral disc space. The expandablefusion device 10 is then introduced into the intervertebral space, withthe end having the expansion portion 334 of the central ramp 18 beinginserted. In an exemplary method, the fusion device 10 is in theunexpanded position when introduced into the intervertebral space. In anexemplary method, the intervertebral space may be distracted prior toinsertion of the fusion device 10. The distraction provide some benefitsby providing greater access to the surgical site making removal of theintervertebral disc easier and making scraping of the endplates of thevertebral bodies 2, 3 easier.

With the fusion device 10 inserted into and seated in the appropriateposition in the intervertebral disc space, the fusion device can thenexpanded into the expanded position, as best seen in FIG. 42. To expandthe fusion device 10, an instrument is engaged with the head portion 324of the actuator assembly 200. The instrument is used to rotate actuatorassembly 200. As discussed above, actuator assembly 200 is threadinglyengaged with the extension 336 of the central ramp 18; thus, as theactuator assembly 200 is rotated in a first direction, the central ramp18 is pulled toward the actuator assembly 200. In an exemplaryembodiment, the actuator assembly 200 is moved in a linear directionwith the ratchet teeth engaging as means for controlling the movement ofthe actuator assembly 200 and the central ramp 18. As the central ramp18 is pulled towards the actuator assembly 200, the first rampedportions 344 of the central ramp 18 push against the second rampedportions 310, 312 of the second endplate 16 and the second rampedportions 346 of the central ramp 18 push against first ramped portions306, 308 of the first endplate 14. In this manner, the central ramp 18acts to push the endplates 14, 16 outwardly into the expanded position.This can best be seen in FIGS. 40-42. As the endplates 14, 16 moveoutwardly the tongues 316, 318, 320, 322 in the endplates 14, 16 ride inthe angled grooves 348, 350 with the tongues 320, 322 in the secondendplate 16 riding in angled grooves 348 and the tongues 316, 318 in thefirst endplate 14 riding in angled grooves 350.

As discussed above, the actuator assembly 200 also engages driving ramp300; thus, as the actuator assembly 200 is rotated in a first direction,the actuator assembly 200 pushes the driving ramp 300 towards thecentral ramp 18 in a linear direction. As the driving ramp 300 is pushedtowards the central ramp 18, the first ramped portions 370 of thedriving ramp 300 push against the first ramped portions 306, 308 of thesecond endplate 16 and the second ramped portions 372 of the drivingramp 300 push against the second ramped portions 310, 312 of the firstendplate 14. In this manner, the driving ramp 300 also acts to push theendplates 14, 16 outwardly into the expanded position. This can best beseen in FIGS. 40-42. As the endplates 14, 16 move outwardly the tongues316, 318, 320, 322 in the endplates 14, 16 ride in the angled grooves370, 372 with the tongues 316, 318 in the second endplate 16 riding inangled grooves 370 and the tongues 320, 322 in the first endplate 14riding in angled grooves 372.

Since the expansion of the fusion device 10 is actuated by a rotationalinput, the expansion of the fusion device 10 is infinite. In otherwords, the endplates 14, 16 can be expanded to an infinite number ofheights dependent on the rotational advancement of the actuator assembly200.

Referring now to FIGS. 50-54, an alternative embodiment of theexpandable fusion device 10 is shown. In the illustrated embodiment, thefusion device 10 includes a first endplate 14, a second endplate 16, acentral ramp 18, an actuator assembly 200, and a driving ramp 300. Aswill be discussed in more detail below, the actuator assembly 200functions, in an embodiment, to pull the central ramp 18 and the drivingramp 300 together, which forces apart the first and second endplates 14,16. In an embodiment, the expandable fusion device may contain features,such as a through bore, that facilitate placement down an endoscopictube. In an embodiment, the assembled fusion device 10 may be placeddown the endoscopic tube and then expanded.

Although the following discussion relates to the first endplate 14, itshould be understood that it also equally applies to the second endplate16 as the second endplate 16 is substantially identical to the firstendplate 14 in embodiments of the present invention. It should beunderstood that, in an embodiment, the first endplate 14 is configuredto interlock with the second endplate 16. With additional reference toFIG. 55, in an exemplary embodiment, the first endplate 14 has a firstend 39 and a second end 41. As illustrated, the first end 39 may bewider than the second end 41. In the illustrated embodiment, the firstendplate 14 further comprises an upper surface 40 connecting the firstend 39 and the second end 41, and a lower surface 42 connecting thefirst end 39 and the second end 41. As best seen in FIG. 54, the lowersurface 42 can be curved concavely such that the first and secondendplates 14, 16 form a through bore when the device 10 is in a closedposition. In an embodiment, the first endplate 14 may comprise a throughopening 44. The through opening 44, in an exemplary embodiment, is sizedto receive bone graft or similar bone growth inducing material.

In one embodiment, the upper surface 40 of the first endplate 14 is flatand generally planar to allow the upper surface 40 of the endplate 14 toengage with the adjacent vertebral body 2. Alternatively, as shown inFIG. 15, the upper surface 40 can be curved convexly or concavely toallow for a greater or lesser degree of engagement with the adjacentvertebral body 2. It is also contemplated that the upper surface 40 canbe generally planar but includes a generally straight ramped surface ora curved ramped surface. The ramped surface allows for engagement withthe adjacent vertebral body 2 in a lordotic fashion. As illustrated, inan exemplary embodiment, the upper surface 40 includes texturing to aidin gripping the adjacent vertebral bodies. For example, the uppersurface 40 may further comprise texturing 400 to engage the adjacentvertebral bodies. Although not limited to the following, the texturingcan include teeth, ridges, friction increasing elements, keels, orgripping or purchasing projections.

In one embodiment, the first endplate 14 further comprises a first sideportion 202 connecting the first end 39 and the second end 41, and asecond side portion 204 connecting the first end 39 and the second end41. In the illustrated embodiment, the first and second side portions202, 204 are extensions from the lower surface 42. In an embodiment, thefirst and second side portions 202, 204 each include an interior surface302 and an exterior surface 304. In an embodiment, the first end 39 ofthe first endplate 14 is generally designed and configured to fit overthe second end 41 of the second endplate 16 when the device 10 is in aclosed position. As illustrated, the first and second side portions 202,204 each may include first ramped portions 306, 308, second rampedportions 310, 312, and/or central ramped portion 402.

In an embodiment, the first ramped portions 306, 308 are proximate thefirst end 39 of the endplate 14. In accordance with embodiment of thepresent invention, the first ramped portions 306, 308 of the firstendplate 14 are generally designed and configured to fit over the secondramped portions 310, 312 of the second endplate 16 when the device 10 isin a closed position. In an exemplary embodiment, the first rampedportions 306, 308 generally face the first end 39 and can extend in anoblique direction with respect to the upper surface 40, for example. Asillustrated, the first ramped portions 306, 308 may include tongueportions 316, 318 extending in an oblique direction with respect to theupper surface 40 of the endplate 14.

In an embodiment, the second ramped portions 310, 312 are proximate thesecond end 41 of the endplate 14. In an exemplary embodiment, the secondramped portions 310, 312 can extend in an oblique direction with respectto the upper surface 40 and generally face the second end 41. The firstand second side portions 202, 204, in an embodiment, each can include abridge portion 314 connecting the first ramped portions 306, 308 and thesecond ramped portions 310, 312. As further illustrated, the secondramped portions 310, 312 may include tongue portions 320, 322 thatextend in an oblique direction with respect to the upper surface 40 ofthe endplate 14.

In an embodiment, the endplate 14 further may include a central rampedportion 402 proximate the bridge portion 314. In the illustratedembodiment, the endplate 14 includes a central ramped portion 402proximate the bridge portion 314 of the second side portion 204. In anexemplary embodiment, the central ramped portion 402 can extend in anoblique direction with respect to the upper surface 40 and face thefirst end 39 of the endplate 14. As illustrated, the first rampedportions 306, 308 may include tongue portions 316, 318 with the tongueportions 316, 318 extending in an oblique direction with respect to theupper surface 40 of the endplate 14.

With reference to FIGS. 50-52 and 54, in an embodiment, the actuatorassembly 200 includes a head portion 324, an extension 404, and athrough bore 406 that extends longitudinally through the actuatorassembly 200. As illustrated, the head portion 324 may include one ormore instrument gripping features 330 that can allow it to be turned bya suitable instrument. In addition, the head portion 324 has a largerdiameter than the other components of the actuator assembly 200 toprovide a contact surface with the driving ramp 300. In the illustratedembodiment, the head portion 324 includes a rim 332 that provides asurface for contacting the driving ramp 300. In an embodiment, theextension 404 is a generally rod-like extension. In another embodiment,the extension 404 includes ratchet teeth for engaging the extension 336.

With reference to FIGS. 51, 52, and 56, the central ramp 18 has a firstend 408 and a second end 410. In an embodiment, the central ramp 18includes a first expansion portion 412, a second expansion portion 414,a rod-receiving extension 416, and a through bore 418 that extendslongitudinally through the central ramp 18. In an exemplary embodiment,first expansion portion 412 can be proximate the first end 408 of thecentral ramp 18. As best seen in FIG. 56, the first expansion portion412 may include side portions 420, 422. In an embodiment, each of theside portions 420, 422 includes dual, overlapping ramped portions thatextend in oblique directions with respect to the through bore 418. Forexample, side portions 420, 422 each include a first ramped portion 424that overlaps a second ramped portion 426. In the illustratedembodiment, the first ramped portion 424 faces the rod-receivingextension 416 while the second ramped portion 426 faces the oppositedirection. In one embodiment, angled grooves 428, 430 are formed in eachof the first and second ramped portions 424, 426. In an exemplaryembodiment, the angled grooves 428, 430 are sized to receive thecorresponding tongues 316, 318, 320, 322 in the first and secondendplates 14, 16 with angled grooves 428 receiving tongues 320, 322 inthe second endplate 16 and angled grooves 430 receiving tongues 316, 318in the first endplate 14. Although the device 10 is described withtongues 316, 318, 320, 322 on the endplates 14, 16 and angled grooves428, 430 on the central ramp 18, it should be understood that thatdevice 10 can also be configured with grooves on the endplates 14, 16and tongues on the central ramp 18, in accordance with one embodiment ofthe present invention.

In an embodiment, the second expansion portion 414 is located on therod-receiving extension 416 between the first end 408 and the second end410 of the central ramp 18. In an exemplary embodiment, the secondexpansion portion 414 includes central ramped portions 432. In oneembodiment, the second expansion portion 414 includes two central rampedportions 432 on opposite sides of the rod-receiving extension 416. In anexemplary embodiment, the central ramped portions 424 extend in anoblique direction with respect to the through bore 418 and face thesecond end 410 of the central ramp 18.

The rod-receiving extension 416 extends from the first expansion portion412 and has an opening 434 at the second end of the central ramp 18. Inan embodiment, the rod-receiving extension 416 is sized and configuredto receive the extension 404 of the actuator assembly 200. In anembodiment, the rod-receiving extension 416 has threading with therod-receiving extension 416 threadingly receiving extension 404 of theactuator assembly 200. In another embodiment, the rod-receivingextension 416 has ratchet teeth with the extension 404 being ratchetedinto the rod-receiving extension 416.

With reference to FIGS. 50-52 and 57, in an exemplary embodiment, thedriving ramp 300 includes an upper portion 354 having an upper surface356 and an oblique surface 358. In an embodiment, the driving ramp 300further includes a bore 366, in an exemplary embodiment, sized toreceive the extension 404 of the actuator assembly 200. In theillustrated, embodiment, the upper portion 354 has a hole 436 thatextends through the upper surface 356 to the bore 366. Set screw 438 maybe inserted through the hole 436 to secure the driving ramp 300 to theactuator assembly 200. In one embodiment, the driving ramp 300 furtherincludes contact surface 368 that engages the rim 332 of the headportion 324 of the actuator assembly 200. In the illustrated embodiment,the contact surface 368 has a generally annular shape.

In an embodiment, the driving ramp 300 further includes side portions360, 362 that extend from the upper portion 354 connecting the upperportion 354 with the lower portion 364 of the driving ramp 300. In anexemplary embodiment, the side portions 360, 362 of the driving ramp 300each include a ramped portion 438. In the illustrated embodiment, theramped portion 438 faces central ramp 300. In an embodiment, the rampedportion 438 is configured and dimensioned to engage the ramped portions306, 308 at the first end 39 of the second endplate 16. In oneembodiment, angled grooves 440 are formed in the ramped portions 316,318. In an exemplary embodiment, the angled grooves 440 are sized toreceive the corresponding tongues 316, 318 in the second endplate 16.Although the device 10 is described with tongues 316, 318 on the secondendplate 16 and angled grooves 440 on the driving ramp 300, it should beunderstood that that device 10 can also be configured with grooves onthe second endplate 16 and tongues on the driving ramp 300, inaccordance with one embodiment of the present invention.

A method of installing the expandable fusion device 10 of FIGS. 50-57 isnow discussed in accordance with one embodiment of the presentinvention. Prior to insertion of the fusion device, the disc space maybe prepared as described above. The expandable fusion device 10 can thenbe inserted into and seated in the appropriate position in theintervertebral disc space. In an embodiment, the device 10 is assembledprior to insertion. The expandable fusion device 10 can be introducedinto the intervertebral space, with the end having the first end 408 ofthe central ramp 18 being inserted. In an exemplary method, the fusiondevice 10 is in the unexpanded position when introduced into theintervertebral space. In an exemplary method, the intervertebral spacemay be distracted prior to insertion of the fusion device 10. Thedistraction provide some benefits by providing greater access to thesurgical site making removal of the intervertebral disc easier andmaking scraping of the endplates of the vertebral bodies 2, 3 easier.

With the fusion device 10 inserted into and seated in the appropriateposition in the intervertebral disc space, the fusion device can thenexpand into the expanded position. To expand the fusion device 10, aninstrument is engaged with the head portion 324 of the actuator assembly200. The instrument is used to rotate actuator assembly 200. Asdiscussed above, actuator assembly 200 is threadingly engaged with therod receiving extension 416 of the central ramp 18; thus, as theactuator assembly 200 is rotated in a first direction, the central ramp18 is pulled toward the actuator assembly 200. In an exemplaryembodiment, the actuator assembly 200 is moved in a linear directionwith the ratchet teeth engaging as means for controlling the movement ofthe actuator assembly 200 and the central ramp 18.

As the central ramp space 18 is pulled towards the actuator assembly200, the central ramp 18 acts to push endplates 14, 16 outwardly intothe expanded position. By way of example, the first ramped portions 424,second ramped portions 426, and central ramped portions 432 push againstthe corresponding ramped portions in the first and second endplates 14,16. The first ramped portions 424 in the first expansion portion 412 ofthe central ramp 18 push against the second ramped portions 310, 312 ofthe second endplate 16 with the corresponding tongues 320, 322 in thesecond ramped portions 310, 312 of the second endplate 16 riding inangled grooves 428 in the first ramped portions 424 in the firstexpansion portion 412. The second ramped portions 426 in the firstexpansion portion 412 push against the first ramped portions 316, 318 ofthe first endplate 14 with the corresponding tongues 316, 318 in firstramped portions 316, 318 of the first endplate 14 riding in angledgrooves 430 in the second ramped portions 426 in the first expansionportion 412. The central ramped portions 432 in the second expansionportion 414 push against the central ramped portion 402 in the first andsecond endplates 14, 16.

As discussed above, the actuator assembly 200 also engages driving ramp300; thus, as the actuator assembly 200 is rotated in a first direction,the actuator assembly 200 pushes the driving ramp 300 towards thecentral ramp 18 in a linear direction. As the driving ramp 300 is pushedtowards the central ramp 18, the driving ramp 300 also acts to push theendplates 14, 16 outwardly into the expanded position. By way ofexample, the ramped portions 438 of the driving ramp 300 push againstramped portions 306, 308 at the first end 39 of the second endplate 16.As the endplates 14, 16 move outwardly, the tongues 316, 318 in theramped portions 306, 308 of the second endplate 16 ride in the angledgrooves 440 in the ramped portions 438 of the driving ramp 300.

It should also be noted that the expansion of the endplates 14, 16 canbe varied based on the differences in the dimensions of the variousramped portions in the central ramp 18, the driving ramp 300, and thefirst and second endplates 14, 16. As best seen in FIG. 16, theendplates 14, 16 can be expanded in any of the following ways: straightrise expansion, straight rise expansion followed by a toggle into alordotic expanded configuration, or a phase off straight rise into alordotic expanded configuration.

In the event the fusion device 10 needs to be repositioned or revisedafter being installed and expanded, the fusion device 10 can becontracted back to the unexpanded configuration, repositioned, andexpanded again once the desired positioning is achieved. To contract thefusion device 10, the instrument can be used to rotate the actuatorassembly 200 in a second direction that is opposite the first direction.Rotation of the actuator assembly 200 results in movement of the centralramp 18 and the driving ramp 300 away from one another. As the centralramp 18 and the driving ramp 300 move, the endplates 14, 16 moveinwardly into the unexpanded position.

Although the preceding discussion only discussed having a single fusiondevice 10 in the intervertebral space, it is contemplated that more thanone fusion device 10 can be inserted in the intervertebral space. It isfurther contemplated that each fusion device 10 does not have to befinally installed in the fully expanded state. Rather, depending on thelocation of the fusion device 10 in the intervertebral disc space, theheight of the fusion device 10 may vary from unexpanded to fullyexpanded. It should be noted that, as well as the height being variedfrom an unexpanded state to an expanded state, the fusion 10 may bepositioned permanently anywhere between the expanded state and theunexpanded state.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

What is claimed is:
 1. A method of installing intervertebral implants,the method comprising: placing more than one intervertebral implant intoan intervertebral disc space, each intervertebral implant comprising: afirst endplate having a first end and a second end, the first endplatecomprising a first side portion and a second side portion; a secondendplate having a first end and a second end, wherein the first end ofthe second endplate is configured to fit over the second end of thefirst endplate, wherein the first end of the first endplate isconfigured to fit over the second end of the second endplate, the secondendplate comprising a first side portion and a second side portion; acentral ramp having a first end and a second end, the central rampcomprising: a bore extending through the central ramp; a first expansionportion at the first end of the central ramp, the first expansionportion comprising a first side portion and a second side portion; anextension, the extension extending from the first expansion portion tothe second end of the central ramp; a second expansion portion locatedon the extension between the first end and the second end of the centralramp; and a driving ramp; rotating the actuator assembly of at least oneof the implants in a first direction to expand the intervertebralimplant such that the implants are implanted at different heights; andwherein in at least one of the implants: the first and second sideportions of the first endplate comprise first ramped surfaces proximatethe first end of the first endplate, and wherein the rotation of theactuator assembly causes first ramped surfaces in the first and secondside portions of the first expansion portion of the central ramp to pushagainst the first ramped surfaces in the first and second side portionsof the first endplate to push the first endplate outwardly; the firstand second side portions of the second endplate comprise second rampedsurfaces proximate the second end of the second endplate, and whereinthe rotation of the actuator assembly causes second ramped surfaces inthe first and second side portions of the central ramp to push againstthe second ramped surfaces in the first and second side portions of thesecond endplate to push the second endplate outwardly; the first andsecond side portions of the second endplate comprise first rampedsurfaces proximate the first end of the second endplate, and whereinrotation of the actuator assembly causes ramped surfaces in the firstand second side portions of the driving ramp to push against the firstramped surfaces in the first and second side portions of the secondendplate to push the second endplate outwardly; the first and secondendplates comprise central ramped surfaces between the first end and thesecond end of the first and second endplates, and wherein rotation ofthe actuator assembly causes ramped surfaces in the second expansionportion to push against the central ramped surfaces in the first andsecond endplates to push the first and second endplates outwardly. 2.The method of claim 1, wherein one or more of the intervertebralimplants placed into the intervertebral disc space are placed down anendoscopic tube.
 3. The method of claim 1, wherein in at least one ofthe implants, the first endplate is configured to interlock with thesecond endplate.
 4. The method of claim 1, wherein in at least one ofthe implants, the first end of the first endplate is wider than thesecond end of the first endplate.
 5. The method of claim 1, wherein inat least one of the implants, the first endplate further comprises alower surface that extends between the first end and the second end ofthe first endplate, wherein the lower surface is curved concavely. 6.The method of claim 1, further comprising inserting bone growth inducingmaterial into at least one of the intervertebral implants.
 7. The methodof claim 1, wherein in at least one of the implants, the first endplatefurther comprises an upper surface that extends between the first endand the second end of the first endplate, wherein the upper surface isplanar.
 8. The method of claim 7, wherein in at least one of theimplants, the upper surface is textured and includes one or more teeth,ridges, friction increasing elements, or keels.
 9. The method of claim1, wherein in at least one of the implants, the actuator assemblyincludes a head portion and an extension portion.
 10. The method ofclaim 9, wherein the head portion includes a rim that provides a surfacefor contacting the driving ramp.
 11. The method of claim 9, wherein theextension portion includes ratchet teeth.
 12. The method of claim 1,wherein in at least one of the implants, the second expansion portionincludes two central ramped portions.
 13. The method of claim 1, whereinin at least one of the implants, the driving ramp includes an upperportion having an upper surface and an oblique surface.
 14. The methodof claim 1, wherein in at least one of the implants, the driving rampfurther includes a bore sized to receive the actuator assembly.
 15. Themethod of claim 1, wherein in at least one of the implants, the drivingramp further includes side portions, wherein each of the side portionseach include a ramped portion.